It is generally known that harvested or prepared food can be kept in a palatable, edible condition longer if stored in an enclosure that inhibits entry and/or circulation of air across the surface of the food. In a simple form, plastic containers having interference-fit lids partially achieve this goal at very low cost. Rigid containers having threads adjacent an opening for receiving a counter-threaded lid are also well known, such as glass jars having metal, threaded lids. Further still, rigid containers may be provided with sealing lids that are otherwise forced onto or clamped against the opening of the container, such as through the use of an external spring clamp or other deformable member. Yet while all such mechanisms prevent the flow of air into or out of a container, they also serve to seal a certain quantity of air within the container itself.
For many years, people have practiced the food preservation technique known as canning in which the food to be stored and the respective container are raised to an elevated temperature before an airtight lid is secured against the container opening. It is often recommended that for best results, as much of the container's interior space should be taken up by the food to be preserved, thus displacing air within the container itself. An airtight seal is thus achieved, but only through significant effort, employment of heating means such as a large water bath, racks or stands for retaining the containers within the heated bath, and scrupulously cleaned containers and lids, and use of great care and patience. While sealing the container and its contents at an elevated temperature results in a slight vacuum under the respective lid once the container and contents are cooled, the effort and logistics required are substantial and absent proper technique spoilage may still occur.
A more simple and effective technique has been identified for food storage. A lid, configured for air-tight sealing of a respective container, is provided with a hand-operated bellows mechanism for evacuating a significant amount of air from the closed container. To achieve such vacuum conditions, the bellows mechanism includes a first one-way valve for enabling air to flow out of the bellows and into the surrounding atmosphere when the bellows is compressed by manual depression of an upper contact surface. Once fully compressed and manual pressure is released, the bellows retracts upward through the force of a resilient member such as a spring. This creates a lower pressure state compared to that within the container itself. A second one-way valve associated with the bellows lid allows air from within the container to flow into the bellows until pressure is equalized. This process is repeated until the pressure within the container is lowered to a point where it is equal to that within the bellows.
Prior art bellows have typically employed a central, axially disposed spring. Such an arrangement, however, is susceptible to frictional interference between the bellows and the lid frame surrounding the bellows when an off-axis component of compressive force is non-negligible. This can be frustrating to a user who perceives a greater amount of force is required to achieve evacuation of the food container than would otherwise be required. This could lead to excessive application of force which may result in breakage of the bellows mechanism.
A further deficiency associated with prior art bellows-enabled container lids is the mechanism for releasing the vacuum state within the container. In a simplest approach, the prior art has employed a projecting member with a knob or other grippable member. The member acts as a manually actuatable valve. A user is required to grip or grasp the knob and pull against the force of the vacuum pressure until a sealing member is disengaged and air is allowed to rush into the container. Such an embodiment may also utilize a resilient member or members such as a spring surrounding the projecting member for urging the sealing member into a sealing position. In that such containers may be employed in wet or oily environments where food is being prepared, grasping such a projecting member and pulling with sufficient force to overcome the vacuum in the container may be difficult.
Alternative techniques for vacuum release have employed complex rotatable arms or levers which translate rotational movement into linear movement, including depression of a one-way valve. The complexity associated with such prior art approaches increases cost, likelihood of material failure, and potential for contamination.
What is lacking in the art is a simple bellows-enabled lid for vacuum sealing a food container, the bellows enabling easy and reliable use even with off-axis manual pressure, and having a simplified vacuum release mechanism that can be operated even in wet or oily environments.